1. Field of the Invention:
The present invention relates to audio equipment. More specifically, the present invention relates to loudspeakers typically used in audio systems.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art:
Loudspeaker design is currently a mature art. For certain applications or tastes, an active speaker system may be preferred over a passive speaker system. Active speaker systems differ from passive systems in that active systems incorporate separately powered electronic circuits (i.e., power amplifiers and the like) for amplification and/or conditioning of signals applied thereto.
As active speaker systems are typically more expensive than passive speaker systems, the performance improvements must be evaluated in relation to the higher cost associated with the active speaker system. The designer of the active system is therefore challenged to design the speaker and the cabinet for optimal performance within certain design constraints. That is, an optimal design requires some interaction between the characteristics of the speaker, the power amplifier, and those of the cabinet and alignment values. For this purpose, the designer must assume either that the characteristics of a speaker are fixed and constant or vary within a limited range.
However, it is known that speaker characteristics actually change as a function of one or more parameters including age, power amplifier output impedance, operating temperature, materials of construction and etc. These parameters may vary independently or dependently further complicating design. For this reason, certain elements may be incorporated into the system to compensate, at least to a degree, for variations in the operating characteristics of speaker and cabinet alignment. These measures generally call for the use of compensation networks and the like.
One such network is an interface between the power amplifier and the speaker. The interface is a control loop with positive current feedback to generate a negative output impedance in the power amplifier. While these systems have been effective in allowing for the use of a large, high Q speaker in a small cabinet, this approach has been subject to some difficulties. Specifically, systems constructed with this approach tended to have a limited bandwidth and may oscillate at higher frequencies, Accordingly, this approach has been limited to use with sub-woofers.
Thus, a need exists in the art for an active speaker design and methodology therefor which would allow for the use of inexpensive components while providing improved performance over a wide bandwidth.